The present invention relates to a speaker and a method for manufacturing the same, in particular to a dome speaker having a dome-shaped vibrating diaphragm and a method for manufacturing the same.
It is known that a speaker for use in an audio system is usually a converter capable of converting an electric signal (an electric energy from an amplifier) to an audio signal (a sound energy).
According to operational principles, commercially available speakers may be classified into a dynamic speaker, an electro static speaker, a piezoelectric speaker, an ionic speaker (ionophone), a magnetic speaker. In fact, the dynamic speaker is a most widely used type because of its good sound quality and some other advantages.
In detail, a dynamic speaker further includes a cone speaker and a dome speaker, both of which are capable of vibrating their vibrating diaphragms by virtue of voice coils provided in their magnetic circuits. But, there is a difference between these two types of speakers. In a cone speaker, its voice coil is driven at a cone neck of a conic vibrating diaphragm. In a dome speaker, since its vibrating diaphragm has a generally dome shape, its voice coil is driven on the outside of the circumference of a dome-shaped diaphragm.
However, in a dome speaker, since its voice coil has a diameter which is almost the same as that of its vibrating diaphragm, the vibrating diaphragm is difficult to be made large in its diameter. On the other hand, since a dome speaker is driven by a voice coil having almost the same diameter as that of a vibrating diaphragm, a relatively large driving force may be obtained for the speaker even if the vibrating diaphragm has a relatively small diameter. For this reason, a dome speaker is often used as a high frequency speaker having a small diameter vibrating diaphragm or a low frequency speaker having a small diameter vibrating diaphragm in a multi-speaker system. Further, it may be used as a receiver in a portable telephone for which a compact size is required.
Usually, a vibrating diaphragm of a dome speaker has a coil holder which is integrally formed with an edge damper that is provided for elastically supporting the vibrating diaphragm. Such a coil holder is proved to be useful for improving an operational efficiency when assembling a speaker device, ensuring that each element may be located at a predetermined position in the assembled speaker with a high precision.
FIG. 6 is a cross sectional view schematically indicating a structure of a dome speaker which employs the above mentioned vibrating diaphragm. As shown in FIG. 6, the dome speaker includes a yoke 101 having a pole section 101a, a ring-shaped magnet 102, a plate 103, thus forming a magnetic circuit having an annular magnetic gap. Further, a generally spherical dome-shaped vibrating diaphragm 104 is provided above the pole section 101a of the yoke 101.
FIG. 7 is an enlarged cross sectional view partially indicating the speaker of FIG. 6, illustrating an area close to the outer edge of the dome-shaped vibrating diaphragm 104. As shown in FIG. 7, along the outer edge of the vibrating diaphragm 104 is formed an annular coil holder 105 having a U-shaped cross section. Connected with the annular coil holder 105 on its outer edge is an annular edge damper 106. In practice, the dome-shaped vibrating diaphragm 104, the annular coil holder 105 and the annular edge damper 106 are integrally formed in connection with one another by heat-pressing a single one piece of a resin film.
Referring to FIG. 6, the edge damper 106 is attached on the plate 103 by connecting its outer edge to an annular projection 103a formed on the plate 103, in a manner such that it can elastically support the vibrating diaphragm 104 and the coil holder 105, enabling the coil holder 105 to be floatingly supported within the annular magnetic gap of the magnetic circuit.
The coil holder 105 contains a voice coil 107 formed by winding a wire into a cylindrical configuration. Such a voice coil 107 is fixed within the coil holder 105 by means of an adhesive 108.
In this way, the voice coil 107 together with the coil holder 105 are allowed to be floatingly supported within the magnetic gap of the magnetic circuit, by means of the edge damper 106. The two ends of the voice coil 107 are respectively let out of the magnetic circuit, so as to be connected to a positive terminal (not shown) and a negative terminal (not shown).
A frame cover 109, which is formed by either a metal or a resin, is provided above the coil holder 105 and the edge damper 106, so as to protect them from a possible damage which will otherwise be caused by an impact from the outside. Further, the frame cover 109 is formed with a plurality of through holes 109a which are used to adjust a reproducing frequency of a sound output emitted from the vibrating diaphragm 104.
With the voice coil 107 fixed within the voice holder 105, and with the outer edge portion of the edge damper 106 connected to the projection 103a of the plate 103, the vibrating diaphragm 104, the coil holder 105, the voice coil 107, the edge damper 106, may be easily and correctly positioned with respect to the magnetic circuit.
Since a dome speaker is compact in size and easy to be assembled, it has been used as a receiver in a portable telephone. Further, since there has been a demand for a more compact portable telephone having a smaller thickness, a dome speaker for use in such portable telephone is also required to be made more compact in size and thinner in its thickness.
However, in order to manufacture a dome speaker with a small thickness, it is necessary that the height of a generally spherical diaphragm be reduced, since such height has a direct effect on the thickness of a dome speaker. This, however, results in a vibrating diagram having a generally elliptical and spherical shape. Since such a vibrating diaphragm does not have a sufficient strength, a deflection will occur in the diaphragm when reproducing an audio signal having a high frequency.
Further, when assembling a dome speaker, since the voice coil 107 is fixed in the coil holder 105 by means of an adhesive 108, the voice coil 107 and the coil holder 105 can not be moved until the adhesive 108 is cured, thus making it difficult for the assembling operation to quickly shift to a next step. As a result, it is difficult to obtain a high efficiency for the assembling operation for assembling a dome speaker.